Improvement in pyrometers



E. BROWN.

Improvement in Pyrometers.

Patented Aug.27,1872.

R ////////My/////// "(,TNrrED STATES PATENT OFFICE.

EDI/VARI) BROWN, OF PHILADELPHIA, PENNSYLVANIA.

IMPROVEMENT IN PYROMETERS.

Specification fortuin g part of Letters Patent No. 130,895, dated August27,1872.

To all whom it may concern:

Be it known that I, EDWARD BEowN, of 311 Walnut street, Philadelphia, inthe State of Pennsylvania, have invented certain new and lusefulImprovements in Pyrometers, of which the following is a specification:

My invention is applicable to all kinds of Apyrometers, but as itrelates more especially to such as are used in liquid baths I willdescribe the same more particularly as applied to such. A greatdifficulty with pyrometers used in liquid baths has been theincorrectness of their indication, arising from the variations of thelevel of the liquid in the baths, wherebya larger or a smaller surfaceof the metal stem is exposed to the heat of the liquid, and consequentlya varyiu g amount of the metal expanded, which, of course, results in alike variation in the indication, for if a larger surface or amount ofthe metal is exposed to the heat it will, of course, expand more inlength than will a smaller surface or amount of the metal with the samedegree of heat. My improvement is designed to overcome this difficulty;and to this end my said invention consists in making the upper portionof the interior expanding material of a pyrometer-which is surrounded byand held in a metal stem-of the same material as the said stem, or amaterial having nearly equal expansion, in order that the interiorindicating and outer surrounding stem will expand equally above a givenpoint, which may be the lowest level of a liquid bath, so that, if thelevel of the liquid rises above the point where this equality ofmaterial of the inner and outer stem commences, the equal expansion ofboth will insure the correctness of the indication.

The accompanying drawing represents avertical section of apyrometer-stem having my improvement applied thereto.

Within the hollow iron-stem R short bars, T, of porcelain or plumbago,are placed, which extend only to wit-hin a certain distance below agiven point-for instance, the ring s, below which -the level of the bathnever falls, but above which it varies. Onthe bars T I place a tube orbar, t', of the same material or a material of nearly equal expansion asthe stem It, so that any heat exerted on the stem above the bars T willexpand the inner bar or tube t equally with the stem R. If, therefore,the stem is inserted in a liquid bath the level of which rises above thering s, the difference of expansion between the bars T and the stem Ralone will be indicated, as the expansion of the bar or tube b is alwaysequal to that of the stem R.

It will be readily understood that the amount of expansion of thedifferently expanding materials makes no difference in the correctindication of the heat, provided there is no variation in the relativeamount of expansion of the two materials; and this I eifect by makingthe expansion of the inner bar and of the outer stem perfectly evenabove a given point--for instance, the lowest level of the liquid-or, inother words, by neutralizing the expansion of one by the equal expansionof the other above a given point, thus merely indicating the differenceof expansion between a certain amount of one material and a certainamount of another. This improvement is ofthe utmost value in pyrometers,as it gives certainty and reliability to indications of high degrees ofheat, which heretofore were only approximately correct, and in manycases absolutely Wrong and unreliable; and this improvement is notmerely applicable to pyrometers used for indicating the temperature ofliquids of varying level,

but it is applicable and highly advantageous to all pyrometers, whetherhaving an iron stem or one of highly refractory material, so long as theinner and outer stem, above a certain and given point-to be determinedby circumstances in different usesare both made of the same material, orof materials of nearly'the same expansive quality.

From the foregoing it will be observed that the inner bar of the stem isformed part o plumbago and part of iron or other similar metal to theouter tube as regards expansibility, so that the upper part of the stem,composed of tube and rod of the same expansibility, will not indicateany effect of heat applied above where the plumbago terminates, and thuseffect a new combination, which entirely avoids the difficultyheretofore existing in pyrometers of the varying level of fluids,

&c., being heated, giving varying,` and uncertain indications by reasonof there being greater expansive matter exposed to the saine degree ofheat at some times than at others.

Having described my invention, I claim- The construction ofpyrolneter-stelns with the top section of the inner bars made of thesame material, or of material of nearly the saine expansive quality asthe outer tube, so that the inner bar and outer tube of the stem expandequally under heat above a given point on the stem, which point isdesigned to be Within the influence of the heated Huid or space to betested to attain the advantages herein described, viz., the correctindication of the temperature of the matter to be indicated. y

EDVD BROVN.

Witnesses:

A. E. H. JOHNSON, ALEX. A. C. KLAUCKE.

